In order to improve the anti-interference ability of permanent magnet synchronous motor speed control system, a robust H∞ control method is proposed. Firstly, according to the principle of robust H∞ control, the design method of permanent magnet synchronous motor speed control is proposed, and the solution method is introduced. The tracking performance, disturbance suppression, output limitation and model uncertainty are considered when designing the weighting function. The influence of the performance weighting function on the dynamic performance is illustrated in detail by means of the Bode diagram, and the design method of the weighting function is given. Then, in order to further improve the disturbance rejection of the system by considering the parameter uncertainty and unmodeled dynamics, the disturbance is observed as a feedforward compensation through the Luenberger observer and feed back into the speed controller to accelerate the dynamic response and enhance the disturbance rejection. Finally, the traditional proportional-integral controller, H∞ speed controller, and the proposed composite speed controller are compared by experiments, and the effectiveness of the proposed speed controller are verified by the experimental results.